Video conferencing systems exist today, and their use will become more widespread as time progresses. In a typical video conferencing system, all participants in the conference, who are present at different locations, are equipped with video cameras, video displays, audio microphones and audio speakers. This equipment allows the users to see and speak with each other, as though present at a single conference table, in a single room.
In addition, the video cameras and displays allow a participant to present materials of interest to the other participants, such as documents or physical objects, as though making a live, personal presentation.
In general, setting up a video conference requires some delays, for several reasons. One is that computers are involved in handling the audio and video signals used in the conference. These computers must, of course, be operative, which requires that they be switched on. Switching-on requires that they run through their initialization routines, which takes time.
Even if the computers are up-and-running, and require no switching, nevertheless, in establishing the video conference, the computer at each participant's location must do things such as (1) agree on modes of data transfer with another computer and (2) run preliminary tests of data transfer, and of certain equipment. Thus, establishing a video conference can require a delay of a few seconds, if the computers are up-and-running, or a minute or more, if the computers must be initialized.
Further, the delay is in addition to the inherent small delay in placing a telephone call. The computers must dial telephone numbers, and wait for other computers to answer the calls.
Therefore, because of the delays inherent in establishing a video conference, it is expected that people will first make an exploratory telephone call, in order to inquire whether a video conference is possible.
It is expected that people will not, in general, attempt an unannounced video conference, because of the time required in setting up the conference. This set-up time will be wasted if the conference fails to be held.
Restated, until technology advances to the point where the time required for initializing video conferences becomes minimal, people will avoid making "cold" video conference calls, and will instead make exploratory audio calls first.
Two additional factors also suggest that exploratory calls will be made prior to video calls. (1) Establishing a video call is somewhat intrusive, in the sense that a video image of the called person becomes immediately available to the caller. Thus, it is possible that, in practice, people will suspend the video transmission abilities of their conference systems, most of the time.
With this suspension, time would be wasted by a caller in attempting to establish a video call: the call will not succeed. Consequently, a caller is expected to make an exploratory audio call first, to ascertain whether video transmission has been suspended and, if so, to request that it be re-enabled.
(2) At present, the cost of making a video call is greater than the cost of making an audio call, because data transmission is more expensive than voice transmission.
Independent of the preceding reasons for making exploratory audio calls, it is expected that parties to ordinary telephone calls would like the ability to transmit visual images, of articles such as documents and physical objects. In general, switchover to a video call is required to accomplish this transmission, unless a video call was made initially.